1. Field of the Invention
The present invention relates to a solid-state image capture device having a plurality of pixels and a first substrate and a second substrate in which circuit elements constituting the pixels are disposed and which are electrically connected by a connection unit, and an image capture device.
2. Description of the Related Art
In recent years, video cameras, electronic still cameras, and the like have come into wide general use. In such cameras, charge coupled device (CCD)-type and amplification-type solid-state image capture devices are used. An amplification-type solid-state image capture device guides signal charges generated and accumulated by a photoelectric conversion unit of a pixel on which light is incident to an amplification unit provided for the pixel, and the amplification unit outputs an amplified signal from the pixel. In the amplification-type solid-state image capture device, a plurality of such pixels are disposed in the form of a two-dimensional matrix. The amplification-type solid-state image capture device is, for example, a complementary metal oxide semiconductor (CMOS)-type solid-state image capture device using a CMOS transistor, and the like.
Typically, in a general CMOS-type solid-state image capture device, a method of sequentially reading out signal charges generated by the photoelectric conversion units of respective pixels arranged in the form of a two-dimensional matrix row by row is employed. In this method, an exposure timing at the photoelectric conversion unit of each pixel is determined by the start and the end of reading out of signal charges, and thus respective rows have different exposure timings. For this reason, when such a CMOS-type solid-state image capture device is used to capture a subject in rapid movement, the subject is distorted in a captured image.
In order to remove this distortion of a subject, a simultaneous image capture function (a global shutter function) that realizes simultaneity of accumulation of signal charges has been proposed. Also, uses of a CMOS-type solid-state image capture device having the global shutter function are increasing. In the CMOS-type solid-state image capture device having the global shutter function, signal charges generated by photoelectric conversion units are generally stored until a readout is performed, and thus it is necessary to have a storage capacitor unit having a light-blocking property. After exposing all pixels simultaneously, such an existing CMOS-type solid-state image capture device simultaneously transfers signal charges generated by respective photoelectric conversion units to respective storage capacitor units in all the pixels to temporarily store the signal charges, and sequentially converts the signal charges into pixel signals to read out the pixel signals at a predetermined readout timing.
However, in the existing CMOS-type solid-state image capture device having the global shutter function, it is necessary to manufacture the photoelectric conversion units and the storage capacitor unit on the same plane of the same substrate, and an increase in a chip area is not avoidable. Further, there is a problem in that, during a standby time until the signal charges accumulated in the storage capacitor unit are read out, the quality of a signal is degraded by noise resulting from light or noise resulting from a leakage current (dark current) generated in the storage capacitor unit.
In order to solve this problem, Japanese Unexamined Patent Application, First Publication No. 2012-257095 (hereinafter referred to as Patent Literature 1) discloses a method of preventing an increase in a chip area and reducing noise by means of a solid-state image capture device in which a first substrate having photoelectric conversion units formed therein and a second substrate having analog memories (corresponding to sample hold capacities of the present invention) formed therein to accumulate signal charges generated by the photoelectric conversion unit are bonded together. In the solid-state image capture device disclosed in Patent Literature 1, a clamp capacitor for removing noise, such as reset noise generated in the first substrate and the like, by a sample hold operation is installed. Also, in the solid-state image capture device disclosed in Patent Literature 1, the clamp capacitor is shared by four pixels.
Patent Literature 1 does not disclose how the sample hold capacities which accumulate signal charges and the clamp capacitor for removing noise are disposed. FIG. 13A and FIG. 13B show an example of the disposition of the sample hold capacities and the clamp capacitor when the second substrate is seen two-dimensionally. Four sample hold capacities 1231, 1232, 1233, and 1234 corresponding to four respective pixels and a clamp capacitor 1260 shared by the four pixels have a structure in which two sheets of flat plate-shaped electrodes (an upper electrode and a lower electrode) formed of a metal are opposite to each other. In order to increase a gain for a signal, the area of the clamp capacitor 1260 is larger than the areas of the sample hold capacities 1231, 1232, 1233, and 1234.
In FIG. 13A, parasitic capacitances C101, C102, C103, C104, C105, C106, C107, and C108 are shown. The parasitic capacitance C101 is a parasitic capacitance between the sample hold capacitor 1231 and the clamp capacitor 1260. The parasitic capacitance C102 is a parasitic capacitance between the sample hold capacitor 1232 and the clamp capacitor 1260. The parasitic capacitance C103 is a parasitic capacitance between the sample hold capacitor 1233 and the clamp capacitor 1260. The parasitic capacitance C104 is a parasitic capacitance between the sample hold capacitor 1234 and the clamp capacitor 1260. The parasitic capacitance C105 is a parasitic capacitance between the sample hold capacitor 1231 and the sample hold capacitor 1232. The parasitic capacitance C106 is a parasitic capacitance between the sample hold capacitor 1232 and the sample hold capacitor 1233. The parasitic capacitance C107 is a parasitic capacitance between the sample hold capacitor 1233 and the sample hold capacitor 1234. The parasitic capacitance C108 is a parasitic capacitance between the sample hold capacitor 1234 and the clamp capacitor 1260.
Since the sample hold capacities 1231, 1232, 1233, and 1234 are formed in almost the same shape and the distances between the sample hold capacities 1231, 1232, 1233, and 1234 and the clamp capacitor 1260 are almost the same, the parasitic capacitances C101, C102, C103, and C104 are almost the same. Also, since the sample hold capacities 1231, 1232, 1233, and 1234 are formed in almost the same shape and the distances between the sample hold capacities 1231, 1232, 1233, and 1234 are almost the same, the parasitic capacitances C105, C106, and C107 are almost the same. However, since the shape of the clamp capacitor 1260 differs from the shapes of the sample hold capacities 1231, 1232, 1233, and 1234, the parasitic capacitance C108 differs from the parasitic capacitances C105, C106, and C107.
In FIG. 13B, parasitic capacitances C111, C112, C113 and C114 are shown. The parasitic capacitance C111 is a parasitic capacitance between a sample hold capacitor 1231 and a sample hold capacitor 1232. The parasitic capacitance C112 is a parasitic capacitance between the sample hold capacitor 1232 and a sample hold capacitor 1233. The parasitic capacitance C113 is a parasitic capacitance between the sample hold capacitor 1233 and a sample hold capacitor 1234. The parasitic capacitance C114 is a parasitic capacitance between the sample hold capacitor 1234 and a clamp capacitor 1260.
Since the sample hold capacities 1231, 1232, 1233, and 1234 are formed in almost the same shape and the distances between the sample hold capacities 1231, 1232, 1233, and 1234 are almost the same, the parasitic capacitances C111, C112, and C113 are almost the same. However, since the shape of the clamp capacitor 1260 differs from the shapes of the sample hold capacities 1231, 1232, 1233, and 1234, the parasitic capacitance C114 differs from the parasitic capacitances C111, C112, and C113.